Manufacturers of engines meet set emissions regulations via aftertreatment systems. Tier 3, Interim Tier 4, and Final Tier 4 emissions regulations, for example, required substantial reductions in particulate matter (“PM”) and nitrogen oxides (“NOx”). Beyond the Final Tier 4 emissions regulation, drivers for the continued evolution of aftertreatment systems may include more stringent emissions standards; lower ownership costs (in particular, the initial cost of purchase); and more compact, modular solutions. Some aftertreatment systems include a diesel particulate filter for reducing PM and a selective catalytic reduction (“SCR”) catalyst for removing NOx. Such systems may have relatively high ownership costs and require relatively large design spaces.
One solution for potentially lowering the costs and minimizing the design spaces of such systems is to instead utilize a selective catalytic reduction on-filter (“SCR+F”). The “SCR+F” includes a diesel particulate filter with a selective catalytic reduction catalyst applied thereto. SCR+F solutions, however, introduce some operational challenges, one of which is that the reactions between the passive regeneration of PM by NOx, and the conversion of NOx by selective reaction with ammonia (“NH3”) are in competition.